1. Field of the Invention
The present invention relates to an apparatus for sealing two substrates of a field emission device and a method therefor.
2. Description of the Related Art
FIG. 1 is a sectional view of a conventional field emission device. As shown in FIG. 1, a plurality of cathodes 2 are formed on a rear surface substrate 1 in the conventional field emission device. A plurality of microtips 2' are formed on the cathodes 2 in an array pattern. The microtips 2' are formed in throughholes 3a of an insulating layer 3 formed on the cathodes 2. Gates 4 having an opening 4a corresponding to the throughhole 3a are stacked on the insulating layer 3. A front surface substrate 6 is provided on the gates 4, supported by spacers 8 spaced from each other by a predetermined distance. A plurality of anodes 5 are formed on the front surface substrate 6 so as to oppose the microtips 2'. Fluorescent films 7 are formed on the anodes 5. Each microtip array of the rear surface substrate (one of these is circled in the drawing) corresponds to a cathode of an electron gun of a CRT. The portion coated with a fluorescent film of the front surface substrate corresponds to an anode formed on the glass screen of a CRT.
When the microtip array of the field emission device is grounded and a uniform voltage is applied between the gates 4 and the anodes 5, electrons are emitted into a vacuum towards the anodes 5. The electrons are accelerated by the voltage of the anodes 5 and collide with a fluorescent film 7 with a predetermined kinetic energy. The kinetic energy of the electrons is transmitted to the fluorescent film 7. The fluorescent film 7 receives the kinetic energy of the electrons and is excited, emitting light.
In the field emission device having such a structure, the edges of the two substrates 1 and 6 are sealed to maintain a vacuum therebetween. FIG. 2 shows the two substrates before sealing. Here, optical fibers 9 are arranged near the edges of the rear surface substrate 1 in order to seal the two substrates. A getter tubulation hole 11 is formed near an edge of the rear surface substrate 1. As shown in FIG. 3, frit is sealed on the inner surface of the optical fiber 9 in a chamber (not shown).
However, in such an apparatus for sealing the substrates, the surfaces of the electrodes (cathodes and anodes) of the two substrates are not effectively outgassed, since pumping is performed through only the getter tubulation hole 11. The life of the field emission device is shortened since a surface processing is hard to perform. Also, since a thermal control (TC) gauge (not shown) is spaced from the surface of the anodes 5 without being attached thereto, a thermal control is not correct. Accordingly, a sealing condition is not good. The substrates are easily broken when tipping is performed, since a supporting holder for supporting the substrates is not provided.